The invention pertains to a longitudinal seat adjustment, especially for vehicle seats, with two pairs of rails, spaced a certain distance apart, namely, an upper rail facing the seat and a lower rail facing the floor of the vehicle; with U-shaped sections on the sidepieces of the two rails, extending in the longitudinal direction, the sections on the lower rail lying in the interior of the rail, whereas those on the upper rail lie outside the U-shaped rail; and with at least one spring-loaded, movable, plate-shaped locking part, which is supported on the upper rail and which, when in the locking position, prevents the upper rail from moving in the lower rail. The exposed edges of the U-shaped sections of the U-shaped lower rail are provided with tooth-like slots, whereas the U-shaped upper rail carries slit-like openings on the sidepieces with the U-shaped sections, into which openings the teeth of the locking part engage, where the locking part can be moved against the force of a spring from a locking position to a released position by the use of an operating element.
A similar form of this type of longitudinal seat adjustment is described in the unpublished Patent Application No. 100 41 605.5 of Aug. 24, 2000.
The task of the invention is to design a longitudinal seat adjustment of the type indicated above in such a way that the peaks of impact-like loads are reduced, so that the person sitting on the seat is protected. The arrangement is also intended to be as simple in design as possible.
This task is accomplished according to the invention in that the edge areas of the tooth-like slots of the lower rail and/or the edge areas of the slit-like openings in the upper rail are designed to be plastifiable, that is, permanently deformable. Here the teeth of the locking part engaging in the openings and in the slots when in the locking position deform the edge areas when a heavy, impact-like load occurs.
Because the edge areas are designed to be deformable or plastifiable, excessive load peaks are reduced. Nevertheless, the pair of rails and the seat, of the motor vehicle are held securely in place. It is recommended that the controlled deformation of the edge areas be accomplished through a perforation of the sidepiece walls of the rails provided with the slots and/or openings. As a result, the rail remains sufficiently strong in spite of the perforation, whereas the perforation has the effect of allowing the edge areas to give way to such an extent that load peaks are reduced; additional locking parts, furthermore, arrive in the path of the forces. A design such as this does not increase the cost of installation.
In a special exemplary embodiment of the invention, a receiving space is provided on each side of the slit-like openings or slots in the rail; the deformed edge areas are thus able to escape into these spaces. This measure means that, when deformation occurs, it can occur over a longer distance and also that, even though the seat is still being held securely, load peaks can continue to be reduced.
Depending on the design, these receiving spaces can be in the form of slots or hourglasses. In another exemplary embodiment, they have at least one transverse web in order to give support to the two adjacent edge areas in the receiving space, as a result of which the forces are transmitted and absorbed more effectively. In another exemplary embodiment, the receiving space is divided by a diagonal web. This diagonal web again allows the deformed areas to be received reliably. The plastifying area can also consist of at least one separate component of different material.
In a special exemplary embodiment, the locking part is divided into at least three individual plates, each of which is equipped with locking teeth on two opposite sides. The individual locking plates make it possible for the locking position to be established securely but also ensures a reliable transmission of force when loads are applied. In a special exemplary embodiment, at least two locking plates, when in their locking position, lie simultaneously in the path of the forces flowing through the upper rail to absorb those forces, so that, as a result of the plastifying effect which occurs under a heavy, impact-like load, the contact angles of the plates with the edge areas undergo hardly any change. This arrangement makes it possible, when the plastifying effect occurs, for the plates themselves to remain in their position and to resist being moved concomitantly, even though the edge areas of the openings in the upper rail, into which the teeth of the locking parts engage, are deformable. The locking plates can hold the seat in its locked position. Because the contact angle does change or changes only slightly, there is also no danger that one or more of the individual plates or all of the plates will become disengaged.
In another exemplary embodiment of the invention, the width of the tooth-like slot in the lower rail is greater than the width of the slit-like opening in the upper rail. If the locking part is divided into at least three separate, movable plates, the teeth of at least two of these plates will be engaged, when in the locking position, with the slots and openings in the rails; in this case, the width of the slit-like openings in the upper rail is the same as the width of the teeth on the locking plate.
As a result of this measure, an almost infinitely variable adjustment of the upper and lower rails with respect to each other is possible. In addition, it is ensured that at least two plates will be in engagement with the lower rail when the locking part is in the locking position. Crash-like loads can thus be efficiently absorbed.